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Vintage and Classic Binoculars discussion (Part 3)

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#1226 Profguy

Profguy

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Posted 04 October 2020 - 01:37 PM

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Hello all, I just picked these up yesterday, Sears Discoverer 8 - 17x40 zoom bins. Everything looks clean and clear, and it has pleasing views, at least in daylight. Too many clouds last night to test on stars. I finally located the J-B46 manufacturer code inside the left barrel, behind the objective lens. After a few minutes of operation and examination, I noticed that the two eyepieces wiggle from side to side as a unit. Also, as I wiggle the eyepieces, the focus knob rotates about a half degree or so, always to the left. I removed the plastic cap on the bottom, then the slotted aluminum screw, then the interior screw and was able to remove the eyepieces. Nothing appears loose. I removed the small screw holding the inter pupillary angle indicator on top of the eyepiece axle, and the nut underneath it appears tight. Upon reassembly, the wiggle seems slightly reduced, but I could be imagining that. Any ideas on what I might need to do to eliminate (or at least reduce) the wiggle?  Also, I noticed that when I adjust the focus and diopter ring at 8 x, and then zoom to 12 or 14 x, the diopter ring will need to be readjusted for optimal focus. Is this normal for these less expensive bins, or could that have something to do with the eyepiece wiggle? Thanks for any and all suggestions/ info!



#1227 sneeds

sneeds

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Posted 05 October 2020 - 04:45 PM

I like those bins Profguy!

For the diopter adjustment, I have found on some zoom binos that this does happen. They are generally not parfocal at different magnifications, which is one of the reasons some people aren't a fan. Sometimes you get lucky and you don't have to do the diopter when zooming - just the centre focus.

The rocking bridge you describe is likely a shortcoming of the build and not because it is a zoom model. Hopefully, in use, this is a minor drawback (mostly noticeable when you are testing them and not looking through them). Tightening the centre focus can help sometimes to reduce the slip...

#1228 Profguy

Profguy

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Posted 05 October 2020 - 08:14 PM

Thanks for the info! I removed the bridge again today and examined things more closely. The tubes that extend upward from the barrels, (that the eyepieces slip over) terminate in a lip. It seemed to me that the lip should stabilize the eyepieces as they move up and down during focusing. I cut three narrow strips of electrical tape and stuck them equidistant around the left tube, starting at the top of the lip and extending downward. That removed almost all the wiggliness I saw before. I added one strip to the right tube, and that made everything very solid, while still allowing the bridge to move smoothly and easily up and down. If the bins continue to operate smoothly with this fix, I may get some etched PTFE film from McMaster and Carr and super glue it in place. I want to do a lot of testing before I take that step though.


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